5&#39;-O-propionyl and 5&#39;-O-butyryl esters of 2-amino-6-methoxy-9-(β-D-arabinofuranosyl)-9H-purine

ABSTRACT

The 5&#39;-O-proprionyl and 5&#39;-O-butyryl esters of 2-amino-6-methoxy-9-(B-D-arabinofuranosyl)-9H-purine useful as inhibitors of varicella zoster virus.

This is a continuation of application(s) Ser. No. 08/110,487 filed Aug.23, 1993 which is a continuation of 07/725,865, filed Jul. 3, 1991, nowU.S. Pat. No. 5,424,295, which is a continuation of Ser. No. 07/444,178,filed Nov. 30, 1989 now abandoned which is a continuation in part ofSer. No. 07/200,022, filed May 27, 1988 now abandoned.

FIELD OF THE INVENTION

The present invention relates to certain substituted purine arabinosidesand physiologically acceptable derivatives thereof, in particularesters, and their use in the treatment of varicella zoster virusinfections.

BACKGROUND OF THE INVENTION

Varicella zoster virus (VZV) which causes chicken-pox and shingles, is aDNA virus of the herpes family. Varicella (chicken-pox) is the primarydisease produced by VZV in a host without immunity; it is usually a mildillness of young children which is manifested as fever and an itchingrash. Herpes zoster (shingles) is the recurrent form of the diseaseoccurring in adults who were previously infected with thevaricella-zoster virus. The clinical manifestations of this infectionare characterized by neuralgia and a vesicular skin rash that isunilateral and dermatomal in distribution. Spread of inflammation maylead to paralysis or convulsions, and coma if the meninges becomeaffected.

SUMMARY OF THE INVENTION

It has now been found that certain purine arabinonucleosides describedbelow characterized by the presence of groups substituted at the 2- and6-positions of the purine ring have potent activity against human virusinfections caused by varicella zoster virus (VZV) and thus are useful intreating such infections including shingles in humans.

Purine arabinonucleosides including 9-β-D-(arabinofuranosyl)-6-methoxy-9H-purine, 9-(β-D-arabinofuranosyl)-6-pyrrolidino-9 H-purine,9-(β-D-arabinofuranosyl)-6-methylamino-9 H-purine and9-(β-D-arabinofuranosyl)-6-dimethylamino-9 H-purine have previously beendescribed in J. Org. Chem. 27, 3274-9 (1962); Cancer Treatment Rep.60(10), 1567-84, (1976); Tetrahedron 40(4), 709-13, (1984); Canada J.Biochem. 4 43(1), 1-15 (1965); J. Med. Chem. 12, 498-504, (1969); J.Biol. Chem. 251(13), 4055-61 (1976); Ann. N.Y. Acad. Sci. 284, 81-90(1977); EP002192; U.S. Pat. No. 3,666,856; U.S. Pat. No. 4,371,613; U.S.Pat. No. 3,758,684; U.S. Pat. No. 4,055,718; U.S. Pat. No. 4,048,432;U.S. Pat. No. 4,055,717.

DETAILED DESCRIPTION OF THE INVENTION

Thus in the first aspect of the present invention there is provided acompound of formula (I): ##STR1## wherein R₁ represents a halogen (e.g.,chlorine or iodine) atom, a C₁₋₅ alkoxy group (e.g., methoxy or ethoxy);halogen-substituted C₁₋₅ alkoxy (e.g., trifluoroethoxy); an amino groupwhich is mono- or di-substituted by C₁₋₅ alkyl (e.g., methyl or ethyl),C₁₋₅ alkyl substituted by one or more fluorine atoms (e.g.,2-fluoroethyl or 2,2,2-trifluoroethyl), or C₃₋₆ cycloalkyl (e.g.,cyclopropyl), or the amino member of a ring containing 4-7 carbon atomsand optionally a double bond (e.g., pyrrolidino) and/or a furthernitrogen atom; and R₂ represents hydrogen, halogen or amino providedthat R₁ is not methoxy or dimethylamino when R₂ is H; andpharmaceutically acceptable derivatives thereof for the treatment ofhuman vital infections caused by VZV.

The present invention also includes the compounds of formula (I) whereinR₂ is hydrogen and R₁ is piperidino or pyrrolidino and wherein R₂ isamino and R₁ is chlorine and the pharmaceutically acceptable derivativesthereof for use in treating VZV infections in humans.

In the above formula (I) the alkyl groups (including those in thealkoxy, alkylamino or dialkylamino groupings) are preferably methyl,ethyl or propyl groups.

Preferred compounds of formula (I) include those wherein:

(a) R₂ is hydrogen; and

(b) R₁ is C₂₋₅ alkoxy; or

(c) R₁ is C₂₋₅ alkylamino; or

(d) R₁ is halogen, e.g., iodo.

The following compounds are preferred compounds of the present inventionby virtue of their potent antiviral activity against VZV;

1) 9-(β-D-Arabinofuranosyl)-6-methylamino-9 H-purine,

2) 9-β-D-Arabinofuranosyl)-6-ethoxy-9 H-purine,

3) 9-(β-D-Arabinofuranosyl)-6-iodo-9 H-purine,

4) 9-(β-D-Arabinofuranosyl)-2-amino-6-iodo-9 H-purine,

5) 9-(β-D-Arabinofuranosyl)-6-pyrrolidino-9 H-purine,

6) 9-(β-D-Arabinofuranosyl)-2-chloro-6-methylamino-9 H-purine,

7) 9-(β-D-Arabinofuranosyl)-6-cyclopropylamino-9 H-purine,

8) 9-(β-D-Arabinofuranosyl)-6-ethyl(methyl)amino-9 H-purine,

9) 9-(β-D-Arabinofuranosyl)-2-amino-6-methoxy-9 H-purine, and

10) 9-(β-D-Arabinofuranosyl)-6-n-propoxy-9 H-purine.

Of the above numbered compounds, compounds 1), 2), 3), 4) and 9) areespecially preferred. The present invention also includes the novelcompounds 2), 3), 4), 6), 7), 8), 9) and 10)listed above.

In a second aspect of the present invention there are provided the novelcompounds of general formula I(a) ##STR2## wherein R₁ represents ahalogen (e.g. chlorine or iodine) atom, a C₁₋₅ alkoxy group (e.g.methoxy or ethoxy); halogen-substituted C₁₋₅ alkoxy (e.g.trifluoroethoxy) an amino group which is mono- or di-substituted by C₁₋₅alkyl (e.g. methyl or ethyl), C₁₋₅ alkyl substituted by one or morefluorine atoms (e.g. 2-fluoroethyl or 2,2,2-trifluoroethyl), or C₃₋₆cycloalkyl (e.g. cyclopropyl) or the amino member of a ring containing4-7 carbon atoms and optionally a double bond (e.g. pyrrolidino) and/ora further nitrogen atom; and R₂ represents hydrogen, halogen or aminoprovided that when R₂ is hydrogen, R₁ does not represent chlorine,methoxy, methylamino, ethylamino, dimethylamino, piperidino orpyrrolidino and when R₂ is amino, R₁ does not represent chlorine ormethylamino; and pharmaceutically acceptable derivatives thereof otherthan the 2',3',5'-triacetate and -tribenzyl derivatives of the compoundsof formula I(a) in which R₁ is chlorine or fluorine when R₂ is chlorine,fluorine, hydrogen or amino.

The present invention further includes a compound of formula I(a) foruse in the treatment of human viral infections caused by VZV.

In a further aspect of the present invention there are providedpharmaceutically acceptable derivatives of the compounds of formula (I)namely any pharmaceutically acceptable ether, ester or salt of suchester, or any other compound which, upon administration to a humansubject is capable of providing (generating) a compound of formula (I)or an antivirally active metabolite thereof in said human as a result ofhuman and/or vital enzymes. Thus the pharmaceutically acceptablederivatives described herein are useful in the treatment of VZVinfections in humans.

The pharmaceutically acceptable esters of the above compounds of formula(I) are particularly preferred since they are capable of providing highlevels of the parent compound of formula (I) or (Ia) in the plasma of asubject after oral administration. The present invention particularlyprovides as a preferred class of novel compounds the pharmaceuticallyacceptable esters formed by esterification of the 2'-, 3'- and/or5'-hydroxy group of the arabino-sugar moiety.

Other preferred derivatives of compounds of formula (I) include mono-di- or tri-esters of the arabino-sugar residue substituted at the 2'-,3'- and 5'-positions of said residue.

Such preferred esters include carboxylic acid esters in which thenon-carbonyl moiety of the ester grouping is selected from straight orbranched chain alkyl (e.g. n-propyl, t-butyl, n-butyl), alkoxyalkyl(e.g. methoxymethyl), aralkyl (e.g. benzyl), aryloxyalkyl (e.g.phenoxymethyl), aryl (e.g. phenyl) optionally substituted by halogen,C₁₋₄ alkyl or C₁₋₄ alkoxy, nitro or amino; sulphonate esters such asalkylsulphonyl; or alkylarylsulphonyl (e.g. methanesulphonyl ortosylsulphonyl); amino acid esters such as aliphatic and aromatic (e.g.aryl) amino acid esters (e.g. Gly, Ala, Leu, lie, Phe, Tyr and Trp) andother natural occurring amino acid esters as well as esters ofβ-alanine; and mono-, di- or triphosphate esters. Pharmaceuticallyacceptable salts of these esters include sodium, potassium, NR₄ ⁺ whereR=H or C₁₋₆ alkyl when the esters contain acidic groups, and acidaddition salts when the esters contain basic (e.g., amino) groups. Inthe above ester groups, the alkyl groups (including those in alkoxygroupings) contain 1 to 12 carbon atoms preferably 1 to 4 carbon atomsand the aryl groups are preferably phenyl.

The purine nucleosides of formula (I) and their derivatives will behereinafter referred to as compounds according to the invention or asactive ingredients.

In a further, preferred aspect of the present invention, there isprovided the use of a compound according to the invention in themanufacture of a medicament for the treatment of human vital infectionscaused by VZV.

The present invention further provides a method for the treatment of VZVinfections in a human subject which comprises administering to the saidhuman subject an effective amount of a compound according to theinvention.

The method hereinbefore described includes inhibiting the replication ofVZV viruses in host cells of a mammal which comprises applying aneffective virus replication inhibiting amount of the compound of formula(I), or a pharmaceutically acceptable derivative thereof, to theinfected cells.

Examples of the clinical conditions caused by VZV infections which maybe treated in accordance with the invention include those referred toabove.

The compound of formula (I) and pharmaceutically acceptable derivativesthereof (hereafter collectively referred to as the active ingredients)may be administered by any route appropriate to the condition to betreated, suitable routes including oral, rectal, nasal, topical(including buccal and sublingual), vaginal and parenteral (includingsubcutaneous, intramuscular, intravenous, intradermal, intrathecal andepidural). It will be appreciated that the preferred route may varywith, for example, the condition of the recipient.

For each of the above-indicated utilities and indications the amountrequired of an active ingredient (as above defined) will depend upon anumber of factors including the severity of the condition to be treatedand the identity of the recipient and will ultimately be at thediscretion of the attendant physician. In general, however, for each ofthese utilities and indications, a suitable, effective dose will be inthe range 0.1 to 250 mg per kilogram body weight of recipient per day,preferably in the range 0.1 to 100 mg per kilogram body weight per dayand most preferably in the range 1 to 20 mg per kilogram bodyweight perday; an optimum dose is about 10 mg per kilogram body weight per day(unless otherwise indicated all weights of active ingredient arecalculated as the parent compound of formula (I); for salts and estersthereof the figures would be increased proportionately). The desireddose is preferably presented as two, three, four or more sub-dosesadministered at appropriate intervals throughout the day. Thesesub-doses may be administered in unit dosage forms, for example,containing 5 to 1000 mg, preferably 20 to 500 mg and most preferably 100to 400 mg of active ingredient per unit dosage form.

While it is possible for the active ingredients to be administered aloneit is preferable to present them as pharmaceutical formulations. Theformulations of the present invention comprise at least one activeingredient, as above defined, together with one or more acceptablecarriers thereof and optionally other therapeutic ingredients. Thecarrier(s) must be "acceptable" in the sense of being compatible withthe other ingredients of the formulation and not deleterious to therecipients thereof.

The formulations include those suitable for oral, rectal, nasal, topical(including buccal and sublingual), vaginal or parenteral (includingsubcutaneous, intramuscular, intravenous, intradermal, intrathecal andepidural) administration. The formulations may conveniently be presentedin unit dosage form and may be prepared by any of the methods well knownin the art of pharmacy. Such methods include the step of bringing intoassociation the active ingredient with the carrier which constitutes oneor more accessory ingredients. In general the formulations are preparedby uniformly and intimately bringing into association the activeingredient with liquid carriers or finely divided solid carriers orboth, and then, if necessary, shaping the product.

Formulations of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, cachets or tabletseach containing a predetermined amount of the active ingredient; as apowder or granules; as a solution or a suspension in an aqueous liquidor a non-aqueous liquid; or as an oil-in-water liquid emulsion or awater-in-oil liquid emulsion. The active ingredient may also bepresented as a bolus, electuary or paste.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compression tablets may be prepared bycompressing in an suitable machine the active ingredient in afree-flowing form such as a powder or granules, optionally mixed with abinder (e.g. povidone, gelatin, hydroxypropylmethylcellulose),lubricant, inert diluent, preservative, disintegrant (e.g. sodium starchglycollate, cross-linked povidone, cross-linked sodium carboxymethylcellulose), surface-active or dispersing agent. Molded tablets may bemade by molding in a suitable machine a mixture of the powdered compoundmoistened with an inert liquid diluent. The tablets may optionally becoated or scored and may be formulated so as to provide slow orcontrolled release of the active ingredient therein using, for example,hydroxypropylmethylcellulose in varying proportions to provide thedesired release profile.

For infections of the eye or other external tissues, e.g., mouth andskin, the formulations are preferably applied as a topical ointment orcream containing the active ingredient in an amount of, for example,0.075 to 20% w/w, preferably 0.2 to 15% w/w and most preferably 0.5 to10% w/w. When formulated in an ointment, the active ingredients may beemployed with either a paraffinic or a water-miscible ointment base.Alternatively, the active ingredients may be formulated in a cream withan oil-in-water cream base.

If desired, the aqueous phase of the cream may include, for example, atleast 30% w/w of a polyhydric alcohol, i.e. an alcohol having two ormore hydroxyl groups such as propylene glycol, butane-1,3-diol,mannitol, sorbitol, glycerol and polyethylene glycol and mixturesthereof. The topical formulations may desirably include a compound whichenhances absorption or penetration of the active ingredient through theskin or other affected areas. Examples of such dermal penetrationenhancers include dimethylsulphoxide and related analogues.

The oily phase of the emulsions of this invention may be constitutedfrom known ingredients in a known manner. While the phase may comprisemerely an emulsifier (otherwise known as an emulgent), it desirablycomprises a mixture of at least one emulsifier with a fat or an oil orwith both a fat and an oil. Preferably, a hydrophilic emulsifier isincluded together with an lipophilic emulsifier which acts as astabilizer. It is also preferred to include both an oil and a fat.Together, the emulsifier(s) with or without stabilizer(s) make up theso-called emulsifying wax, and the wax together with the oil and/or fatmake up the so-called emulsifying ointment base which forms the oilydispersed phase of the cream formulations.

Emulgents and emulsion stabilizers suitable for use in the formulationof the present invention include Tween 60, Span 80, cetostearyl alcohol,myristyl alcohol, glyceryl monostearate and sodium lauryl sulphate. Thechoice of suitable oils or fats for the formulation is based onachieving the desired cosmetic properties, since the solubility of theactive compound in most oils likely to be used in pharmaceuticalemulsion formulations is very low. Thus the cream should preferably be anon-greasy, non-staining and washable product with suitable consistencyto avoid leakage from tubes or other containers. Straight or branchedchain, mono-or dibasic alkyl esters such as di-isoadipate, isocetylstearate, propylene glycol diester of coconut fatty acids, isopropylmyristate, decyl oleate, isopropyl palmitate, butyl stearate,2-ethylhexyl palmitate or a blend of branched chain esters known asCrodamol CAP may be used, the last three being preferred esters. Thesemay be used alone or in combination depending on the propertiesrequired. Alternatively, high melting point lipids such as white softparaffin and/or liquid paraffin or other mineral oils can be used.

Formulations suitable for topical administration to the eye also includeeye drops wherein the active ingredient is dissolved or suspended in asuitable carrier, especially an aqueous solvent for the activeingredient. The active ingredient is preferably present in suchformulations in a concentration of 0.5 to 20%, advantageously 0.5 to 10%particularly about 1.5% w/w.

Formulations suitable for topical administration in the mouth includelozenges comprising the active ingredient in a flavored base, usuallysucrose and acacia or tragacanth; pastilles comprising the activeingredient in an inert base such as gelatin and glycerin, or sucrose andacacia; and mouthwashes comprising the active ingredient in a suitableliquid carrier.

Formulations for rectal administration may be presented as a suppositorywith a suitable base comprising for example cocoa butter or asalicylate.

Formulations suitable for nasal administration wherein the carrier is asolid include a coarse powder having a pardde size for example in therange 20 to 500 microns which is administered in the manner in whichsnuff is taken, i.e. by rapid inhalation through the nasal passage froma container of the powder held close up to the nose. Suitableformulations wherein the carrier is a liquid, for administration as; forexample, a nasal spray or as nasal drops, include aqueous or oilysolutions of the active ingredient.

Formulations suitable for vaginal administration may be presented aspessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining in addition to the active ingredient such carriers as areknown in the art to be appropriate.

Formulations suitable for parenteral administration include aqueous andnon-aqueous sterile injection solutions which may contain anti-oxidants,buffers, bacteriostats and solutes which render the formulation isotonicwith the blood of the intended recipient; and aqueous and non-aqueoussterile suspensions which may include suspending agents and thickeningagents. The formulations may be presented in unit-dose or multi-dosecontainers, for example sealed ampoules and vials, and may be stored ina freeze-dried (lyophilized) condition requiring only the addition ofthe sterile liquid carrier, for example water for injections,immediately prior to use. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules and tabletsof the kind previously described.

The phosphate esters of this invention may be encapsulated in liposomesusing methods well known in the art. The liposome formulations of thesephosphate esters, preferably the monophosphates, most preferably the5'-monophosphates, are included within the scope of this invention.

Preferred unit dosage formulations are those containing a daily dose orunit daily sub-dose, as herein above recited, or an appropriate fractionthereof, of an active ingredient.

It should be understood that in addition to the ingredients particularlymentioned above the formulations of this invention may include otheragents conventional in the art having regard to the type of formulationin question, for example those suitable for oral administration mayinclude flavoring agents.

The present invention also provides a process for the preparation of acompound of formula I(a), or a pharmaceutically acceptable derivative,especially an ester, thereof comprising either:

A. reacting a compound of formula (II) ##STR3## wherein R₁ and R₂ are ashereinbefore defined, with a compound of formula (III) ##STR4## whereinX represents a pyrimidine or purine base (other than a compound offormula (II)); or

B. reacting a compound of formula (IV) ##STR5## wherein Z is a leavinggroup and R₂ is as hereinbefore defined, with a compound capable ofintroducing the necessary group at the 6-position; and optionallythereafter or simultaneously therewith, where the resulting compound isa compound of formula (I), converting it into a pharmaceuticallyacceptable derivative thereof Or where the resulting compound is apharmaceutically acceptable derivative converting it into a differentpharmaceutically acceptable derivative or a compound of formula (I).

With regard to process A), X is advantageously a uracil base. Thereaction may be effected, for example, by treatment of the compounds offormulae (II) and (III) with an enzyme such as a phosphorylase enzyme,for example, a mixture of uridine phosphorylase and purine nucleosidephosphorylase in the presence of inorganic phosphate at an pH of 5.0-9.0and a temperature of 15°-90° C. advantageously 40°-60° C.

Regarding process B) this this may be carried out in accordance with theprocedure described by Reist. E. J. et al., J. Org. Chem. 27 (1962)3274-3279. A convenient leaving group is a halogen atom for examplechlorine, the reaction being advantageously carried out in an organicsolvent, e.g., absolute methanol, with an agent capable of providing thenecessary group at the 6-position for example, an appropriate amine inthe case where R₁ represents an alkyl- or dialkylamino group.

Physiologically acceptable esters and salts of the compounds of formula(I) may be prepared in conventional manner for example esters may beprepared by esterification of the parent compound with an appropriateacyl halide or anhydride. Alternatively the esters may be prepared bydisplacing an appropriate leaving group, e.g., halide, with anappropriate carboxylic acid or by opening an appropriate anhydronucteoside of the parent compound with an appropriate carboxylic acid orsalt thereof.

The following Examples illustrate the present invention but should notbe considered in anyway limiting of the invention.

EXAMPLE 1: 9-β-D-Arabinofuranosyl-6-methylamino-9 H-purine

6-Thiol-9-(β-D-arabinofuranosyl)-9 H-purine (Reist E. J. et al., J. Org.Chem. 27 (1962) 3274-3279) (0.35 mmole, 100 mg) and 5 ml of absolutemethanol were combined and cooled to -10° C. while protected frommoisture. Chlorine gas was bubbled gently through the suspension for 2min. The resulting solution was stirred for 5 min at -10° C. then drynitrogen was bubbled through the cold solution for 15 min until theexcess chlorine was removed. Two milliliters of 40% aqueous methylaminewas added to the reaction mixture, which was then heated in a stainlesssteel bomb at 115° C. for 4.5 hr. The bomb was cooled to 0° C. and thecontents were evaporated to dryness, providing an 88% yield of the titlecompound. After recrystallization in water the sample had a meltingpoint of 201.5°-202.5° C.

EXAMPLE 2: 9-β-D-Arabinofuranosyl-6-ethoxy-9 H-purine

6-Ethoxypurine (Sigma Chemical Co. St. Louis, Mo.) (3.05 mmoles, 0.5 g)and uracil arabinoside (6.09 mmoles, 1.48 g) were suspended in 100 ml ofa 10 mM potassium phosphate, 0.04% potassium azide solution with a pH of7.4. Purified uridine phosphorylase (6000 I.U.) and purine nucleosidephosphorylase (8400 I.U.) (Krenitsky, T. A., et al. Biochemistry, 20,3615 (1981) and U.S. Pat. No. 4,381,344) were added and the suspensionstirred at 35° C.

After 168 hours an additional 18000 units of uridine phosphorylase and75600 units of purine nucleoside phosphorylase were added. Seven dayslater the reaction was filtered and the flitrate chromatographed on acolumn containing Dowex-I-hydroxide resin (2.5×8 cm). The column waseluted with 90% methanol/water (v/v) and fractions containing productwere combined and the solvent removed under vacuum. The residue wasdissolved in 30% n-propanol and water (v/v) and chromatographed on acolumn containing BioRad P-2 (5×90 cm). The product was eluted with 30%n-propanol/water (v/v). Product-containing fractions were combined andthe solvent removed under vacuum, yielding 0.363 g of9-β-D-arabinofuranosyl-6-ethoxy-9 H-purine that analyzed as a 0.3hydrate. NMR and mass spectrometry were consistent with the structure.

Anal. Calcd. for C₁₂ H₁₆ N₄ O₅.0.3H₂ O: Calcd: C, 47.78; H, 5.55; N,18.57. Found: C, 47.99; H, 5.54; N, 18.40.

EXAMPLE 3: 9-β-D-Arabinofuranosyl-6-iodo-9 H-purine

6-Iodopurine (Sigma Chemical Co. St. Louis, Mo.) (4 mmoles, 1 g) wasdissolved in 15 ml of 1,2-dimethoxyethane with heating. Fiftymilliliters of a uracil arabinoside solution (10.1 mmoles)in 10 mMpotassium phosphate, 0.04% potassium azide solution, pH of 7.4, wereadded. Purified uridine phosphorylase (6800 I.U.) and purine nucleosidephosphorylase (12000 I.U.) were added and the reaction stirred at 35° C.After 21 days an additional 4800 units of uridine phosphorylase and20000 units of purine nucleoside phosphorylase were added, Ninety dayslater the reaction was filtered and the solvent removed under vacuum.The residue was suspended in 100 ml of water, heated with steam, andthen filtered. The flitrate was chromatographed on a column containingXAD-2 resin (5×35 cm), eluting with 2 liters of water followed by 2liters ethanol. Fractions containing product were combined-and thesolvent removed under vacuum. The residue was dissolved in 30%n-propanol/water (v/v) and chromatographed on a column containing BioRadFP-2 (5×90 cm). The product was eluted with 30% n-propanol/water (v/v).Product-containing fractions were combined and the solvent removed undervacuum. The residue was dissolved in 30% n-propanol/water (v/v) andchromatographed on a Sephadex G-10 column (5×90 cm). This column waseluted with 30% n-propanol/water (v/v). Product-containing fractionswere combined and after removing the solvent under vacuum, yielded 0.253g of 9-β-D-arabinofuranosyl-6-iodo-9 H-purine that analyzed as a 1.5hydrate. NMR and mass spectrometry were consistent with the structure.

Anal. Calcd. for C₁₀ H₁₁ IN₄ O₄.1.5 H₂ O: Calcd: C, 29.65; H, 3.48; N,13.83; I, 31.32. Found: C, 29.43; H, 3.53; N, 13.66; I, 31.20.

EXAMPLE 4: 9-β-D-Arabinofuranosyl-2-amino-6-iodo-9 H-purine

2-Amino-6-iodopurine (Sigma Chemicals, St. Louis. Mo.) (25.5 mmoles,6.75 g) and uracil arabinoside (61.9 mmoles. 15.1 g) were combined in0.31 liters of 10 mM potassium phosphate pH 6.9 with 0.02% potassiumazide. Purified purine nucleoside phosphorylase (17000 units) anduridine phosphorylase (2000 units) were added and the solution stirredat 37° C. After 18 days an additional 5700 units of uridinephosphorylase were added. Fifty-seven days later the reaction wasfiltered and the flitrate chromatographed on a column containing XAD-2resin (8×11 cm). The product was eluted with a step gradient ofethanol/water (v/v) as follows: 0.35 liter 10%; 1 liter 20%; 1 liter50%; 0.2 liter 95%. Product-containing fractions were combined and theethanol removed under vacuum. The residue was dissolved in 30%n-propanol/water (v/v) and chromatographed on a 7.5×90 cm columncontaining BioRad P-2 resin, This procedure yielded 1.1 g of9-β-D-arabinofuranosyl-2-amino-6-iodo-9 H-purine as a 0.5 hydrate. NMRand mass spectrometry were consistent with the structure.

Anal. Calcd. for C₁₀ H₁₂ IN₅ O₄.0.5H₂ O: Calcd: C, 29.87; H, 3.26; N,17.4. Found: C, 29.86; H, 3.29; N, 17.39.

EXAMPLE 5: 9-β-D-Arabinofuranosyl-6-pyrrolidino-9 H-purine

6-Pyrrolidinopurine (Sigma Chemical Co., St. Louis, Mo.) (2.6 mmoles),0.5 g, and uracil arabinoside (5.29 mmoles, 1.29 g) were suspended in100 ml of a 10 mM potassium phosphate 0.04% potassium azide solutionwith a pH of 7.4. Purified uridine phosphorylase (6000 I.U.) and purinenucleoside phosphorylase (8400 I.U.) (Krenitsky, T. A., et al.Biochemistry, 20, 3615 (1981) and U.S. Pat. No. 4,381,344) were addedand the suspension stirred at 35° C. Twenty days later the reaction wasfiltered and the filtrate chromatographed on a column containingDowex-I-hydroxide resin (2.5×8 cm). The product was eluted from thecolumn with 90% methanol/water (v/v). Fractions containing product werecombined and the solvent removed under vacuum. The residue was dissolvedin 50 ml of 30% n-propanol and water (v/v) and chromatographed on aBioRad P-2 column (5×90 cm). The product was eluted with 30%n-propanol/water (v/v). Product-containing fractions were combined andthe solvent was removed under vacuum yielding 0.573 g of9-β-D-arabinofuranosyl-6-pyrrolidino-9 H-purine. NMR and massspectrometry were consistent with the structure.

Anal. Calcd. for C₁₄ H₁₉ N₅ O₄ : Calcd: C, 52.33; H, 5.96N, 21.79.Found: C, 52.60; H, 6.09; N, 21.51.

EXAMPLE 6: 9-β-D-Arabinofuranosyl-2-chloro-6-methylamino-9 H-purine

A solution of2,6-dichloro-2',3',5'-tri-O-benzyl-9-(β-D-arabinofuranosyl)purine(Keller, F. et al., J. Org. Chem., 32, 1644 (1967); Montgomery, J. A.and Hewson, K. J., J. Med. Chem. 12, 498 (1967)) (5.92 g, 10 mMoles) inbenzene (35 ml of a solution of 0.6 g methylamine per 10 ml benzene) waskept at room temperature in a sealed bomb for 4 days. The bomb wascooled thoroughly in ice, opened, and the contents filtered to removemethylamine hydrochloride. The solvent was removed in vacuo to give anoil that was combined with an oil from a reaction of the same scale, butconducted at 125° C. The total weight was 11.4 g. TLC showed it wasmixture of starting material, mono-and dimethylamino compounds. The oilwas chromatographed on 285 g silica gel using 30% acetone and 70%cyclohexane by volume. The component running below starting material(TLC, silica gel, 3:7 acetone:cyclohexane) was collected and the solventremoved in vacuo. Yield: 4.8 g of2-chloro-6-methylamino-2',3',5'-tri-O-benzyl-9-(β-D-arabinofuranosyl)purine,as an oil. A 1.1 g portion of this in 40 mi 2-methoxyethanol was addedto palladium chloride (0.87 g) that was prereduced in a Parr apparatus.This was hydrogenated at 50 psi for 30 min with the hydrogen atmospherechanged after the initial 15 min. The catalyst was removed by filtrationthrough a bed of Celite and washed with methanol. The filtrate wasneutralized by the addition of Dowex-1 (HCO₃). The resin was removed byfiltration and washed with methanol. The filtrate was evaporated invacuo and the residue triturated with chloroform. The crude product waswashed with hot water, dissolved in hot methanol, filtered, cooled, andthe solid collected. Crystallization from boiling water gave the titlecompound as a hydrate. Yield 44.5 mg; mp 224°-225° C.

Anal. Calcd. for C₁₁ H₁₄ N₅ O₄ Cl.H₂ O: Calcd: C, 39.59; N, 20.99; H,4.83. Found: C, 39.27; N, 20.83; H, 5.16.

EXAMPLE 7: 9-β-D-Arabinofuranosyl-6-cyclopropylamino-9 H-purine

6-Cyclopropylaminopurine (prepared by nucleophilic displacement of thechlorine group on 6-chloropurine (Sigma Chemicals, St. Louis Mo.) bycydopropylamine in acetonitrile) (2.85 mmoles, 0.5 g) and uracilarabinoside (Torrenee, P. F. et al. J. Med. Chem., 22(3), 316-319(1979)) (5.71 mmoles, 1.39 g) were suspended in 100 ml of a 10 mMpotassium phosphate, 0.04% potassium azide solution with a pH of 7.4.Purified uridine phosphorylase (6000 I.U.) and purine nucleosidephosphorylase (8400 I.U.) (Krenitsky, T. A. et al. Biochemistry, 20,3615 (1981) and U.S. Pat. No. 4,381,344) were added and the suspensionstirred at 35° C. After 120 hours the reaction was filtered and thefiltrate chromatographed on a column containing Dowex-I-hydroxide resin(2.5×10 cm). The column was eluted with 90% methanol/water (v/v).Fractions containing product were combined and the solvent removed undervacuum. The residue was dissolved in 30% n-propanol and water (v/v) andchromatographed BioRad P-2 (5×90 cm). The column was eluted with 30%n-propanol/water (v/v). The precipitate from the reaction wasre-crystallized from hot methanol yielding 0.352 g that analyzed as6-cyclopropylaminopurine-9-β-D-arabinofuranoside monohydrate.

Anal. Calcd. for C₁₃ H₁₇ N₅ O₄.H₂ O: Calcd: C, 48.00; H, 5.89; N, 21.53.Found: C, 48.05; H, 5.89; N, 21.55.

The filtrate from the recrystallization was chromatographed on BioRadP-2 (5×90 cm) resin as described above. Product containing fractionsfrom both columns were combined and the solvent removed under vacuumyielding 0.342 g of 9-β-D-arabinofuranosyl-6-cyclopropylamino-9 H-purinethat analyzed as a 0.8 hydrate with 0.3 C₃ H₈ O. NMR and massspectrometry were consistent with the structure.

Anal. Calcd. for C₁₃ H₁₇ N₅ O₄.0.8 H₂ O.0.3 C₃ H₈ O: Calcd: C, 49.14; H,6.23; N, 20.61. Found: C, 48.83; H, 5.88; N, 20.29.

EXAMPLE 8: 9-β-D-Arabinofuranosyl-6-ethyl(methyl)amino-9 H-purine

6-Ethyl(methyl)aminopurine was prepared by nucleophilic displacement ofthe chlorine group on 6-chloropurine (Sigma Chemicals, St. Louis, Mo.)by ethyl-(methyl)amine in acetonitrile. 6-Ethyl(methyl)aminopurine (2.8mmoles, 0.5 g) and uracil arabinoside (5.6 mmoles, 1.38g) were suspendedin 575 ml of a 10 mM potassium phosphate, 0.04% potassium azidesolution, pH of 7.4, containing 10% n-propanol (v/v). Purified uridinephosphorylase (6000 I.U.) and purine nucleoside phosphorylase (8400I.U.) (Krenitsky, T. A. et al., Biochemistry, 20, 3615 (1981) and U.S.Pat. No. 4,381,344) were added and the solution stirred at 37° C.Nineteen days later the reaction was filtered and the filtratechromatographed on a 2.5×13 cm column containing Dowex-1-hydroxideresin. The resin was eluted with 90% methanol/water (v/v). Fractionscontaining the product were combined and the solvent removed undervacuum. The residue was dissolved in 30% n-propanol/water (v/v) andchromatographed on BioRad P-2 column (7.5×90 cm). Product containingfraction were combined and after lyophilization yielded 0.680 g of9-β-D-arabinofuranosyl-6-ethyl(methyl)amino-9 H-Purine. NMR and massspectrometry were consistent with the structure.

Anal. Calcd. for C₁₃ H₁₉ N₅ O₄ : Calcd: C, 50.48; H, 6.19; N, 22.64.Found: C, 50.36; H, 6.25; N, 22.52.

EXAMPLE 9: 9-β-D-Arabinofuranosyl-2-amino-6-methoxy-9 H-purine

2-Amino-6-methoxypurine (prepared by nucleophilic displacement of thechlorine group on 2-amino-6-chloropurine(Sigma Chemicals, St. Louis,Mo.) by methanol with sodium hydride in tetrahydrofuran) (6.4 mmoles,1.05 g) was combined with 35 ml of a uracil arabinoside solution (7.04mmoles, 1.75 g) in 10 mM potassium phosphate and 7% n-propanol (v/v).The pH was adjusted to 6.75. Purified purine nucleoside phosphorylase(18000 units) and uridine phosphorylase (1020 units) were added and thesolution incubated at 37° C. After 26 days the reaction was filtered andthe filtrate chromatographed on a column of Dowex-1-formate resin (2×7cm) after adjusting the pH to 10.5 with concentrated ammonium hydroxide.The column was eluted with 7% n-propanol/water (v/v) and fractionscontaining product were combined and solvent removed in vacuo. Theresidue was extracted with 25 ml of water and the filtrate separatedfrom the solids by centrifugation. The supernatant upon standing atambient temperature formed crystals of9-β-D-arabinofuranosyl-2-amino-6-methoxy-9 H-purine which after dryingin vacuo, yielded 0.327 g of product. NMR and mass spectrometry wereconsistent with the structure.

Anal. Calcd. for C₁₁ H₁₅ N₅ O₅ : Calcd: C, 44.44; H, 5.09; N, 23.56.Found: C, 44.49; H, 5.13; N, 23.52.

EXAMPLE 9A: 2-Amino-6-methoxy-9-(5-O-propionyl-β- D-arabinofuranosyl)-9H-purine

2-Amino-6-methoxy-9-β-D-arabinofuranosyl)-9 H-purine (1.0 g, 3.3 mmol)was suspended in 40 ml of pyridine that contained 300 μL of H₂ O and 2ml of trichloroethyl propionate (Trichloroethyl propionate wassynthesized by addition of 19 ml of propionyl chloride (Aldrich) over 30minutes to 19.1 ml of trichlorethanol (Aldrich) in 40 ml of pyridine at0° C.). The product was purified by successive washing with 2×100 mlaliquots of H₂ O, 5% NaHCO₃, and H₂ O. ¹ H NMR (200 MHz, CDCl₃), 4.74(s, 2 H, Cl₃ CH₂.), 2.49 (q, 2 H, J=7.6 Hz, CH₃ CH₂ CO₂₋₋), 1.21 (t, 3H, J=7.6 Hz, CH₃ CH₂ CO₂₋₋). The reaction was initiated with 0.100 g ofsubtilisin (Sigma Chemical Co., St. Louis, Mo., P-5380, lot #38F-0356),which had been activated by dissolving 1 g of the enzyme in 20 ml of0.1M potassium phosphate at pH 7.8 and lyophilizing to dryness. Afterstirring for 23 hours at 40° C., the reaction was quenched by filteringoff the enzyme and the solvent was removed in vacuo. The crude productwas purified by chromatography on a 4.5×25 cm silica gel column with CH₂Cl₂ :CH₃ OH (9:1) as eluant. Product fractions were pooled andlyophilized from water to yield 0.76 g of the desired product as a whitepowder; m.p. 124° C.; TLC R_(f) =0.43 (silica gel; CH₂ Cl₂ :CH₃ OH(9:1)); UV λ_(max) (.di-elect cons., mM⁻¹ cm⁻¹) at pH 7.0, 278 nm (9.5).¹ H NMR(200 MHz, DMSO-d₆), δ7.83(s, 1 H, H₈), 6.44 (s, 2 H, 2-NH₂), 6.14(s, 1 H, H_(1')), 5.75 (d, 1 H, J=4.3 Hz, 2'-OH), 5.65 (d, 1 H, J=3.5Hz, 3'-OH), 4.28 (m, 2 H, H_(2') and H_(3')), 4.08 (m, 2 H, H_(5')),3.95 (s, 3 H, 6'-OCH₃), 3.91 (m, 1 H, H4'), 2.32 (q, 2 H, J=7.6 Hz, CH₃CH₂ CO₂₋₋), 1.01 (t, 3 H, J=7.5 Hz, CH₃ CH₂ CO₂₋₋); MS (ci) 354 (M+1),280 (M-C₂ H₅ CO₂).

Anal. Calcd. for C₁₄ H₁₉ N₅ O₆.0.46 H₂ O: Calcd: C, 46.49; H, 5.55; N,19.36. Found: C, 46.46; H, 5.52; N, 19.45.

EXAMPLE 9B: 2-Amino-6-methoxy-9-(5-O-butyryl-β-D-arabinofuranosyl)-9H-Purine

2-Amino-6-methoxy-9-β-D-arabinofuranosyl)-9 H-purine (0.50 g, 1.6 mmol)was suspended in 30 ml of pyridine that contained 300 mL of H₂ O and0.52 ml of trichloroethyl butyrate (Trichloroethyl butyrate wassynthesized by addition of 47 g of butyryl chloride (Aldrich) over 30minutes to 67.5 g of trichloroethanol (Aldrich) in 75 mL of pyridine at0° C.). The product was purified by successive washing with 2×200 mLaliquots of H₂ O, 5% NaHCO₃, and H₂ O. ¹ H NMR (200 MHz, CDCl₃) 4.74 (s,2 H, Cl₃ CH₂₋₋), 2.4 (t, 2 H, J=7.3 Hz, CH₃ CH₂ CH₂ CO₂₋₋), 1.72(sextet, 2 H, J=7.5 Hz, CH₃ CH₂ CH₂ CO₂₋₋), 0.99 (t,3 H, J=7.4 Hz, CH₃CH₂ CH₂ CO₂₋₋)). The reaction was initiated with 0.100 g of subtilisin(Sigma Chemical Co., St. Louis, Mo., P-5380, lot #38F-0356), which hadbeen activated by dissolving 1 g of the enzyme in 20 ml of 0.1Mpotassium phosphate at pH 7.8 and lyophilizing to dryness. Afterstirring for 47 hours at 40° C., the reaction was quenched by filteringoff the enzyme and the solvent was removed in vacuo. The crude productwas purified by chromatography on a 4.5×25 cm silica gel column with CH₂Cl₂ :CH₃ OH (85:15) as the eluant. Product fractions were pooled andlyophilized from water to yield 0.27 g of the desired product as a whitepowder; m.p. 105° C.; TLC R_(f) =0.65 silica gel; CH₂ Cl₂ :CH₃ OH(85:15)); UV λ_(max) (.di-elect cons., mM⁻¹ cm⁻¹) at pH 7.0, 279 nm(8.3). ¹ H NMR (200 MHz, DMSO-d₆): δ7.83 (s, 1 H, H₈), 6.46 (s, 2 H,2-NH₂), 6.14 (d, 1 H, J=3.9 Hz, H1'), 5.76 (d, 1 H, J=4.3 Hz, 2'-OH),5.66(d, 1 H, J=3.7 Hz, 3'-OH), 4.28 (m, 2 H, H_(2') and H_(3')), 4.07(m, 2 H, H_(5')), 3.94 (s, 3 H, 6'-OCH₃), 3.91 (m, 1 H, H_(4')), 2.28(t, 2 H, J=7.2 Hz, CH₃ CH₂ CH₂ CO₂₋₋), 1.52 (sextet, 2 H, J=7.4 Hz, CH₃CH₂ CH₂ CO₂₋₋), 0.85 (t, 3 H, J=7.3 Hz), CH₃ CH₂ CH₂ CO₂₋₋); MS (ci) 368(M+1).

Anal. Calcd. for C₁₅ H₂₁ N₅ O₆.0.60 H₂ O: Calcd: C, 47.64; H, 5.72; N,18.52. Found: C, 47.62; H, 5.82; N, 18.53.

EXAMPLE 9C:2-Amino-9-(2,5-di-O-tert-butyldimethylsilyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine.

2-Amino-9-(β-D-arabinofuranosyl)-6-methoxy-9 H-purine (10 g, 34 mmol)was added to a 500 mL round bottom flask and dried by coevaporation withpyridine (2×50 mL). Imidazole (11 g, 160 mmol) was added, followed bytert-butyldimethylsilyl chloride (11 g, 74 mmol). The flask was flushedwith argon and fitted with a septum. Dry dimethylformamide (DMF, 40 mL)was added and the solution was stirred at room temperature for 18 hours.TLC on silica gel with acetone: CHCl₃ (1:10) showed that about 20% ofthe starting material remained (R_(f) =0.05) and that three higher R_(f)spots had formed at 0.18, 0.41 and 0.75. Additionaltert-butyldimethylsilyl chloride (1.0 g, 6.6 mmol) was added andstirring was continued for 24 hours. TLC in the same solventsubsequently showed all the starting material was consumed.

The DMF was then removed under reduced pressure and the residue waspartitioned between ethyl acetate (350 mL) and H₂ O (100 mL and 3×50mL). The aqueous layers were back extracted with ethyl acetate (100 mL)and the combined organic layers were dried (MgSO₄), filtered, andconcentrated. Crude product was purified on a silica gel flash column(5×25 cm) eluted with a step gradient of acetone in CHCl₃ (1:20 to 1:2).Three product fractions were obtained corresponding to the three spotsobserved by TLC. The R_(f) =0.18 fraction provided 4.0 g (23%) of awhite solid identified as the 2,5-disilylated product: m.p.=180°-182° C.(uncorrected); UV λ_(max) (95% EtOH): 248.8 nm and 280.8 nm; MS (EI):m/z 468 (C₁₉ H₃₄ N₅ O₅ Si₂), 450 (C₁₉ H₃₂ N₅ O₄ Si₂), 336 (C₁₃ H₁₈ N₅ O₄Si), 322 (C₁₄ H₂₄ N₅ O₂ Si), 264 (C₁₀ H₁₄ N₅ O₂ Si), 222 (C₈ H₈ N₅ O₃),208 (C₈ H₁₀ N₅ O₂), 194 (C₇ H₈ N₅ O₂), 166 (C₆ H₈ N₅ O), 133 (C₆ H₁₇OSi), 115 (C₆ H₁₅ Si), 57 (C₄ H₉). ¹ H-NMR (CDCl₃): δ7.87 (s, 1 H, H-8),6.29 (d, 1 H, H-1', J=4.6 Hz), 4.82 (brs, 2 H, NH₂), 4.39-4.34 (m, 2 H,H-2' and 3'), 4.07 (s, 3 H, --OCH₃), 3.94-3.82 (m, 3 H, H-4' and 5'),2.40 (brs, 1 H, 3'-OH), 0.91 (s, 9 H, (CH₃)₃ CSi), 0.71 (s, 9 H, (CH₃)₃CSi), 0.09 (s, 6 H, (CH₃)₂ Si), -0.02 (s, 3 H, (CH₃)Si), -0.24 (s, 3 H,(CH₃)Si).

Anal. Calcd. for C₂₃ H₄₃ N₅ O₅ Si₂ : Calcd: C, 52.54; H, 8.24; N, 13.32.Found: C, 52.28; H, 8.20; N, 13.17.

EXAMPLE 9D:2-Amino-9-(2,5-di-O-tert-butyldimethylsilyl-3-O-pivaloyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-[(2,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-6-methoxy-9H-purine (2.0 g, 3.8 mmol) was weighed in to a flame dried 250 mL roundbottom flask. 4-N,N-Dimethylaminopyridine (0.05 g, 0.4 mmol) was addedand the flask was flushed with argon and sealed with a septum. Dryacetonitrile (50 mL), triethylamine (8.0 mL), and pivalic anhydride (3mL, 14.8 mmol) were added to the reaction mixture. After 158 hours, thereaction mixture was concentrated and the residue was taken up in ethylacetate (250 mL) and extracted with H₂ O (3×50 mL). The ethyl acetatewas dried (MgSO₄), filtered, and concentrated to give 3.8 g of a yellowoil. A 300 mg portion of this material was purified on a Chromatotron(Harrison Scientific) fitted with a 4 mm silica gel rotor, eluting withacetone:CHCl₃ (1:10). The product was isolated as a clear gum (0.176 g);MS (EI): m/z 609 (C₂₈ H₅₁ N₅ O₆ Si₂), 594 (C₂₇ H₄₈ N₅ O₆ Si₂), 552 (C₂₄H₄₂ N₅ O₆ Si₂), 450 (C₁₉ H₃₂ N₅ O₄ Si₂), 322 (C₁₄ H₂₄ N₅ O₂ Si), 314(C₁₆ H₃₀ O₄ Si), 194 (C₇ H₈ N₅ O₂), 166 (C₆ H₈ N₅ O), 57 (C₄ H₉). ¹H-NMR (CDCl₃): δ7.93 (s, 1 H, H-8), 6.25 (d, 1 H, H-1', J=3.8 Hz), 5.28(d, 1 H, H-3', J=2.2 Hz), 5.05 (brs, 2 H, NH₂), 4.30 (dd, 1 H, H-2',J_(1'),2' =3.6 Hz and J_(2'),3' =1.8 Hz), 4.10 (s, 3 H, --OCH₃), 4.04(dt, 1 H, H-4', J=2.5 Hz, J=5.9 Hz), 3.19 (d, 2 H, H-5', J=5.5 Hz), 1.27(s, 9 H, --OCOC(CH₃)₃), 0.90 (s, 9 H, --SiC(CH₃)₃), 0.75 (s, 9 H,--SiC(CH₃)₃), 0.09 (s, 6 H, --Si(CH₃)₂), 0.02 (s, 3 H, --Si(CH₃)), -0.33(s, 3 H, --Si(CH₃)).

Anal. Calcd. for C₂₈ H₅₁ N₅ O₆ Si₂.0.75C₃ H₆ O.0.05 CHCl₃ : Calcd: C,55.19; H, 8.49; N, 10.62. Found: C, 55.32; H, 8.61; N, 10.53.

EXAMPLE 9E: 2-Amino-6-methoxy-9-(3-O-pivaloyl-β-D-arabinofuranosyl)-9H-purine

2-Amino-6-methoxy-9-[(3-O-pivaloyl-2,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-9H-purine (2.1 g, 3.4 mmol) was taken up in THF (40 mL) and cooled in anice bath to 5° C. H₂ O (1 mL) was added, followed by tetrabutylammoniumfluoride (TBAF) as a 1M solution in THF (10 mL, 10 mmol). After 2 hoursat 5° C., an additional 10 mL of TBAF was added. After two hours, thereaction was treated with yet an additional 5 mL of TBAF and allowed tostir for eighteen hours more. The reaction mixture was then diluted withCHCl₃ (40 mL) and passed through a pad of silica gel (230-400 mesh, 5×5cm) with 1:1 acetone:CHCl₃ (500 mL). The filtrate was concentrated andadded to a silica gel column (230-400 mesh, 5×18 cm). The column waseluted with a step gradient of acetone in CHCl₃ (1:10 to 1:1acetone:CHCl₃). Two main fractions were obtained from the columncorresponding to material with an R_(f) =0.74 and 0.50 in acetone:CHCl₃(1:1). The lower R_(f) material was isolated as a white powder 0.77 g(53%) and was shown to be the desired 3'-O-pivaloyl derivative: m.p.241°-243° C. (uncorrected); UV λ_(max) (.di-elect cons.): pH=7.00: 278.9nm (8,700) and 247.7 nm (8,900); 0.1N CHl: 287.0 (8,600) and 243.7(6,800); 0.1N NaOH: 279.2 (8,900) and 248.7 (8,200); MS (EI): m/z 381(M, C₁₆ H₂₃ N₅ O₆), 366 (C₁₅ H₂₀ N₅ O₆), 296 (C₁₁ H₁₄ N₅ O₅), 280 (C₁₁H₁₄ N₅ O₄), 250 (C₁₀ H₁₂ N₅ O₃), 232 (C₁₀ H₁₀ N₅ O₂), 208 (C₈ H₁₀ N₅O₂), 194 (C₇ H₈ N₅ O₂), 165 (C₆ H₇ N₅ O), 136 (C₅ H₄ N₄ O), 85 (C₅ H₉O); IR (KBr): 1733.6, 1594.7 cm⁻¹. ¹ H-NMR (Me₂ SO-d₆): δ7.95 (s, 1 H,H-2), 6.45(brs, 2 H, NH₂), 6.10 (d, 1 H, H-1', J=4.3 Hz), 6.10 (d, 1 H,2'-OH, J=5.5 Hz) 5.16-5.10 (m, 2 H, H-3' and 5'-OH), 4.23-4.20 (m, 1 H,H-2'), 3.94 (s, 3 H, Pur-OCH₃), 3.90-3.86 (m, 1 H, H-4'), 3.67-3.60 (m,2 H, 5'), 1.18 (s, 9 H, C(CH₃)₃).

Anal. Calcd. for C₁₆ H₂₃ N₅ O₆.0.40 CHCl₃ : Calcd: C, 45.90; H, 5.50; N,16.32. Found: C, 45.72; H, 5.43; N, 16.04.

EXAMPLE 9F:2-Amino-9-(3,5-di-O-tert-butyldimethylsilyl-2-O-valeryl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-[(3,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-6-methoxy-9H-purine (1.3 g, 2.5 mmol) was weighed into a flame dried 250 mL roundbottom flask. 4-N,N-Dimethylaminopyridine (0.05 g, 0.4 mmol) was addedand the flask was flushed with argon and sealed with a septum. Dryacetonitrile (30 mL), triethylamine (5.0 mL) were added and the solutionwas cooled in an ice bath. Valeric anhydride (0.6 mL, 3.0 mmol) wasadded to the reaction mixture. After 18 hours at 0°-5° C., the reactionmixture was concentrated and the residue was taken up in hexane:ethylacetate (1:1) (200 mL) and extracted with H₂ O (3×50 mL). The organiclayer was dried (MgSO₄) filtered, and concentrated to give 1.7 g of ayellow oil. A 270 mg portion of this material was purified on aChromatotron (Harrison Scientific) fitted with a 2 mm silica gel rotor.The rotor was eluted with acetone:CHCl₃ (1:10). The product off theChromatotron was a white solid (0.21 g, 0.34mmol): m.p.=105°-107° C.(uncorrected); MS(EI): m/z 609 (C₂₈ H₅₁ N₅ O₆ Si₂), 594 (C₂₇ H₄₈ N₅ O₆Si₂), 552 (C₂₄ H₄₂ N₅ O₆ Si₂), 420 (C₁₈ H₂₈ N₅ O₅ Si), 292 (C₁₃ H₁₈ N₅O₃), 261 (C₁₂ H₁₅ N₅ O₂), 231 (C₁₀ H₉ N₅ O₂), 194(C₇ H₈ N₅ O₂), 166 (C₆H₈ N₅ O), 159 (C₇ H₁₅ O₂ Si), 57 (C₄ H₉). ¹ H-NMR (CDCl₃): δ7.92 (s, 1H, H-8), 6.39 (d, 1 H, H-1', J=5.7 Hz), 5.33 (t, 1 H, H-2', J=5.7 Hz),4.84 (brs, 2 H, NH₂), 4.60 (t, 1 H, H-3', J=5.7 Hz), 4.05 (s, 3 H,OCH₃), 3.93-3.80 (m, 1 H, H-4' and H-5'), 2.09 (dt, 1 H, C(O)CH₂, J=7.5Hz), 1.94 (dt, 1 H, C(O)CH₂, J=7.5 Hz, J=15 Hz), 1.32-1.00 (m, 4H, --CH₂CH₂₋₋), 0.93 (s, 9 H, --SiC(CH₃)₃), 0.89 (s, 9 H, --SiC(CH₃)₃), 0.76 (t,3 H, --CH₃, J=7.0 Hz); 0.11 (s, 3 H, Si(CH₃)), 0.09 (s, 3 H, --Si(CH₃)),0.09 (s, 3 H, --Si(CH₃)), 0.08 (s, 3 H, --Si(CH₃)).

Anal. Calcd. for C₂₈ H₅₁ N₅ O₆ Si₂ : Calcd: C, 55.14; H, 8.43; N, 11.48.Found: C, 55.09; H, 8.45; N, 11.46.

EXAMPLE 9G: 2-Amino-6-methoxy-9-(2-O-valeryl-β-D-arabinofuranosyl)-9H-purine

2-Amino-9-(3,5-di-O-tert-butyldimethylsilyl-2-O-valeryl-β-D-arabinofuranosyl)-6-methoxy-9 H-purine (1.4 g, 2.3 mmol) was taken upin tetrahydrofuran (THF, 40 mL) and cooled in an ice bath to 5° C.Acetic acid (0.06 mL, 10 mmol) was added, followed by tetrabutylammoniumfluoride (TBAF) as a 1M solution in THF (10 mL, 10 mmol). After 18 hoursat 5° C., the reaction mixture was diluted with CCHl₃ (40 mL) and passedthrough a pad of silica gel (230-400 mesh, 5×5 cm) with 1:1acetone:CHCl₃ (500 mL).The filtrate was concentrated and purified on aChromatotron fitted with a 4 mm rotor and eluted with neat ethylacetate. Pure product was obtained from the column as a white foam 0.72g (78%) after drying and was shown to be the desired 2'-O-valerylderivative: m.p.: 83°-86° C. (uncorrected); UV λ_(max) (.di-electcons.): pH=7.00: 280.0 nm (7,800), 247.8 nm (8,400); 0.1N HCl: 278.6(8,000), 248.7 (7,400); 0.1N NaOH: 286.2 (7,600), 244.9 (7,200); MS(EI): m/z 381 (C₁₆ H₂₃ N₅ O₆), 351 (C₁₅ H₂₁ N₅ O₅), 292 (C₁₃ H_(:8) N₅O₃), 279 (C₁₁ H₁₃ N₅ O₄), 249 (C₁₀ H₁₁ N₅ O₃), 217 (C₁₀ H₁₇ O₅), 194 (C₇H₈ N₅ O₂), 165 (C₆ H₇ N₅ O), 135 (C₅ H₅ N₄), 85 (C₅ H₉ O). IR (KBr)1745.2, 1613.3 and 1588.7 cm⁻¹. ¹ H-NMR (Me₂ SO-d₆): δ7.93 (s, 1 H,H-2), 6.46 (brs, 2 H, NH₂), 6.26 (d, 1 H, H-1', J=5.9 Hz), 5.79 (d, 1 H,3'-OH, J=5.1 Hz), 5.23 (t, 1 H, H-2', J=5.8 Hz), 5.02 (t, 1 H, 5'-OH,J=5.6 Hz), 4.36 (ddd, 1 H, H-3', J_(3'),3'-OH =5.1 Hz, J_(2'),3' =5.7Hz, J_(3'),4' =5.8 Hz), 3.93 (s, 3 H, Pur-OCH₃), 3.83-3.78 (m, 1 H,H-4'), 3.68-3.61 (m, 2 H, H-5'), 2.09 (dt, 1 H, C(O)CH₂, J=7.5 Hz, J=15Hz), 1.93 (dt, 1 H, C(O)CH₂, J=7.5 Hz, J=15 Hz), 1.30-0.90 (m, 4H, --CH₂CH₂ --), 0.65 (t, 3 H, --CH₃, J=7 Hz).

Anal. Calcd. for C₁₆ H₂₃ N₅ O₆.0.15 C₅ H₁₀ O₃ : Calcd: C, 50.41; H,6.22; N, 17.29. Found: C, 50.41; H, 6.59; N, 17.40.

EXAMPLE 9H:2-Amino-9-(3-O-benzoyl-2,5-di-O-tert-butyldimethylsilyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-[(2,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-6-methoxy-9H-purine (1.5 g, 2.9 mmol) was weighed into a flame dried 250 mL roundbottom flask. 4-N,N-Dimethylaminopyridine (0.05 g, 0.4 mmol) was addedand the flask was flushed with argon and sealed with a septum. Dryacetonitrile (50 mL), triethylamine (5.0 mL), and benzoic anhydride(0.77 g, 3.4 mmol) were added to the reaction mixture. After 5 hours atambient temperature, the reaction mixture was concentrated and theresidue was taken up in ethyl acetate (250 mL) and extracted with H₂ O(2×50 mL). The ethyl acetate was dried (MgSO₄), filtered, andconcentrated to give 3.8 g of a yellow oil. A 270 mg portion of thismaterial was purified on a Chromatotron (Harrison Scientific) fittedwith a 4 mm silica gel rotor. The rotor was eluted with acetone:CHCl₃(1:10). The product off the Chromatotron was a white solid (0.18 g, 0.29mmol): m.p.=73°-75° C. (uncorrected); MS (EI): m/z 630 (C₃₀ H₄₈ N₅ O₆Si₂), 614 (C₂₉ H₄₄ N₅ O₆ Si₂), 572 (C₂₆ H₄₄ N₅ O₆ Si₂), 451 (C₁₉ H₃₃ N₅O₄ Si₂), 194 (C₇ H₈ N₅ O₂), 179 (C₆ H₅ N₅ O₂), 166 (C₆ H₈ N₅ O), 105 (C₇H₅ O). ¹ H-NMR (CDCl₃): δ8.12-8.07 (m, 2 H, Ar-H), 7.92 (s, 1 H, H-8),7.63-7.45 (m, 3 H, Ar-H), 6.33 (d, 1 H, H-1', J=3.7 Hz), 5.46 (t, 1 H,H-3', J=1.8 Hz), 4.79 (brs, 2 H, NH₂), 4.42 (dd, 1 H, H-2', J_(1'2')=3.7 Hz and J_(2'3') =1.7 Hz), 4.30-4.20 (m, 1 H, H-4'), 4.07 (s, 3 H,--OCH₃), 3.99-3.95 (m, 2 H, H-5'), 0.89 (s, 9 H, --SiC(CH₃)₃), 0.76 (s,9 H, --Si(CH₃)₃), 0.09 (s, 6 H, --Si(CH₃)₂), 0.03 (s, 3 H, --Si(CH₃)),-0.34 (s, 3 H, --Si(CH₃)):

Anal. Calcd. for C₃₀ H₄₇ N₅ O₆ Si₂ : Calcd: C, 57.20; H, 7.52; N, 11.12.Found: C, 57.08; H, 7.59; N, 11.05.

EXAMPLE 91: 2-Amino-9-(3-O-benzoyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-(3-O-benzoyl-2,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-6-methoxy-9H-purine (1.97 g, 2.6 mmol) was taken up in tetrahydrofuran (THF, 40 mL)and cooled in an ice bath to 5° C. Acetic acid (0.06 mL, 10 mmol) wasadded, followed by tetrabutylammonium fluoride (TBAF) as a 1M solutionin THF (10 mL, 10 mmol). After 18 hours at 5° C., the reaction mixturewas diluted with CHCl₃ (40 mL) and passed through a pad of silica gel(230-400 mesh, 5×5 cm) with 1:1 acetone:CHCl₃ (500 mL). The filtrate wasconcentrated to a white solid which was adsorbed onto 10 g of silica geland added to a silica gel column (230-400 mesh, 5×18 cm). The column waseluted with acetone:CHCl₃ (1:2). Pure product was obtained from thecolumn corresponding to material with an R_(f) =0.56 in acetone:CHCl₃(1:1). This material was a white powder 0.77 g (1.9 mmol) after dryingand was shown to be the desired 3'-O-benzoyl derivative: rep. 155°-157°C. (uncorrected); UV λ_(max) (.di-elect cons.): pH=7.00: 278.3 nm(10,100), 235.2 nm (18,800); 0.1N HCl: 278.1 (9,100), 245 (sh) (9,600);0.1N NaOH: 284.8(9,600), 233.9 (18,400); MS (EI): m/z 401 (M, C₁₈ H₁₉ N₅O₆), 296 (C₁₁ H₁₄ N₅ O₅), 250 (C₁₀ H₁₂ N₅ O₃), 232 (C₁₀ H₁₀ N₅ O₂), 20(C₈ H₁₀ N₅ O₂), 194 (C₇ H₈ N₅ O₂), 179 (C₇ H₇ N₄ O₂), 165 (C₆ H₇ N₅ O),136 (C₅ H₄ N₅), 122 (C₇ H₅ O₂), 105 (C₇ H₅ O); IR(KBr): 1714.6, 1611.8and 1591.7 cm⁻¹. ¹ H-NMR(Me₂ SO-d₆): δ8.06(s, 1 H, H-2), 8.02-8.00 (m, 2H, Ar-H), 7.71 (t, 1 H, Ar-H, J=7.3 Hz), 7.57 (t, 2 H, Ar-H, J=7.4 Hz),6.45 (brs, 2 H, NH₂), 6.20 (d, 1 H, H-1', J=4.3 Hz), 6.12 (d, 1 H,2'-OH, J=5.5 Hz), 5.41 (t, 1 H, H-3', J=2.9 Hz), 5.20 (t, 1 H, 5'-OH,J=5.5 Hz), 4.43-4.37 (m, 1 H, H-2'), 4.17-4.11 (m, 1 H, H-4'), 3.95 (s,3 H, Pur-OCH₃), 3.79-3.72 (m, 2 H, 5').

Anal. Calcd. for C₁₈ H₁₉ N₅ O₆.0.60 C₃ H₆ O.0.05CHCl₃ :Calcd: C, 53.92;H, 5.16; N, 15.84. Found: C, 53.81; H, 5.10; N, 15.76.

EXAMPLE 9J:2-Amino-9-(3,5-di-O-tert-butyldimethylsilyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-(β-D-arabinofuranosyl)-6-methoxy-9 H-purine (10 g, 34 mmol)was added to a 500 mL round bottom flask and dried by coevaporation withpyridine (2×50 mL). Imidazole (11 g, 160 mmol) was added, followed bytert-butyldimethylsilyl chloride (11 g, 74 mmol). The flask was flushedwith argon and fitted with a septum. Dry dimethylformamide (DMF, 40 mL)was added and the solution was stirred at room temperature for 18 hours.TLC on silica gel with acetone:CHCl₃ (1:10) showed that about 20% of thestarting material remained (R_(f) =0.05) and that three higher R_(f)spots had formed at 0.18, 0.41 and 0.75. Additionaltert-butyldimethylsilyl chloride (1.0 g, 6.6 mmol) was added andstirring was continued for 24 hours. TLC in the same solventsubsequently showed all the starting material was consumed.

The DMF was then removed under reduced pressure and the residue waspartitioned between ethyl acetate (350 mL) and H₂ O (100 mL and 3×50mL). The aqueous layers were back extracted with ethyl acetate (100 mL)and the combined organic layers were dried (MgSO₄), filtered, andconcentrated. Crude product was purified on a silica gel flash column(5×25cm) eluted with a step gradient of acetone in CHCl₃ (1:20to 1:2).Three product fractions were obtained corresponding to the three spotsobserved by TLC. The R_(f) =0.41 fraction provided 8.0 g (45 %) of awhite solid identified as the 3,5-disilylated product: m.p.=88-90° C.(uncorrected); UV λ_(max) (95% EtOH): 247.1 nm and 280.1 nm; MS (EI):m/z 526 (M+H, C₂₃ H₄₄ N₅ O₅ Si₂), 510 (C₂₂ H₄₀ N₅ O₅ Si₂), 468 (C₁₉ H₃₄N₅ O₅ Si₂), 336 (C₁₃ H₁₈ N₅ O₄ Si), 301 (C₁₃ H₂₅ O₄ Si₂), 261 (C₁₁ H₁₁N₅ O₃), 231 (C₁₀ H₉ N₅ O₂), 208 (C₈ H₁₀ N₅ O₂), 194 (C₇ H₈ N₅ O₂), 165(C₆ H₇ N₅ O), 133 (C₆ H₁₇ OSi), 115 (C₆ H₁₅ Si), 57 (C₄ H₉). ¹ H-NMR(CDCl₃): δ8.01 (s, 1 H, H-8), 6.16(d, 1 H, H-1', J=3.1 Hz), 5.08(brs, 1H, 2'-OH), 4.84(brs, 2 H, NH₂), 4.31 (t, 1 H, H-3', J=1.8 Hz), 4.16-4.13(m, 1 H, H-2'), 4.05 (s, 3 H, --OCH₃), 4.02-3.99 (m, 1 H, H-4'), 3.94(dd, 1 H, H-5', J_(4'),5' =3.7 Hz, J_(5'),5" =11.0 Hz), 3.79 (dd, 1 H,H-5", J_(4'),5' =2.7 Hz, J_(5'),5" =11.0 Hz), 0.94 (s, 9 H, (CH₃)₃ CSi),0.93 (s, 9 H, (CH₃)₃ CSi), 0.17 (s, 3 H, CH₃ Si ), 0.14 (s, 3 H, CH₃ Si), 0.12 (s, 6 H, (CH₃)₂ Si).

Anal. Calcd. for C₂₃ H₄₃ N₅ O₅ Si₂ : Calcd: C, 52.54; H, 8.24; N, 13.32.Found: C, 52.32; H, 8.24; N, 13.25.

EXAMPLE 9K:2-Amino-9-(3,5-di-O-tert-butyldimethylsilyl-2-O-pivaloyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-(3,5-di-O-tert-butyldimethylsilyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine (1.3 g, 2.5 mmol) was weighed into a flame dried 250 mL roundbottom flask. 4-N,N-Dimethylaminopyridine (0.05 g, 0.4 mmol) was addedand the flask was flushed with argon and sealed with a septum. Dryacetonitrile (30 mL), triethylamine (50 mL) and pivalic anhydride (0.6mL, 3.0 mmol) were added to the reaction mixture which was stirred atroom temperature. After 160, the reaction mixture was concentrated, theresidue taken up in ethyl acetate (250 mL) and extracted with H₂ O (3×50mL). The ethyl acetate was collected, dried (MgSO₄), filtered, andconcentrated to give 2.0 g of a yellow oil. A 250 mg portion of thismaterial was purified on a Chromatotron® (Harrison Scientific) fittedwith a 2 mm silica gel rotor, eluted with acetone:CHCl₃ (1:10). Theproduct off the Chromatotron® was a clear gum (0.176 g); MS (EI): m/z609 (C₂₈ H₅₁ N₅ O₆ Si₂), 594 (C₂₇ H₄₈ N₅ O₆ Si₂), 552 (C₂₄ H₄₂ N₅ O₆Si₂), 420 (C₁₈ H₂₈ N₅ O₅ Si), 292 (C₁₃ H₁₈ N₅ O₃), 261 (C₁₂ H₁₅ N₅ O₂),231 (C₁₀ H₉ N₅ O₂), 194 (C₇ H₈ N₅ O₂), 166 (C₆ H₈ N₅ O), 159 (C₇ H₁₅ O₂Si), 57 (C₄ H₉). ¹ H-NMR (CDCl₃): δ7.88 (s, 1 H, H-8), 6.40 (d, 1 H,H-1', J=5.9 Hz), 5.30 (t, 1 H, H-2', J=6.0 Hz), 4.85 (br.s, 2 H, NH₂),4.65 (t, 1 H, H-3', J=6.0 Hz), 4.04 (s, 3 H, OCH₃), 3.95-3.85 (m, 1 H,H-4' and H-5'), 0.92 (s, 9 H, OCOC(CH₃)₃), 0.89 (s, 9 H, SiC(CH₃)₃),0.88 (s, 9 H, SiC(CH₃)₃), 0.13 (s, 3 H, SiCH₃), 0.11 (s, 3 H, SiCH₃),0.08 (s, 3 H, SiCH₃), 0.07 (s, 3 H, SiCH₃).

Anal. Calcd. for C₂₈ H₅₁ N₅ O₆ Si₂ : Calcd: C, 55.14; H, 8.43; N, 11.48.Found: C, 54.97; H, 8.42; N, 11.10.

EXAMPLE 9L: 2-Amino-6-methoxy-9-[(2-O-pivaloyl)-β-D-arabinofuranosyl]-9H-purine

2-Amino-6-methoxy-9-(3,5-di-O-tert-butyldimethylsilyl-2-O-pivaloyl-β-D-arabinofuranosyl)-9H-purine (1.3 g, 2.0 mmol) was taken up in tetrahydrofuran (THF, 40 mL)and cooled in an ice bath to 5° C. Acetic acid (0.06 mL, 10 mmol) wasadded, followed by tetrabutylammonium fluoride as a 1M solution in THF(10 mL, 10 mmol). After 24 hours at 5° C., the reaction mixture wasdiluted with CHCl₃ (40 mL) and passed through a pad of silica gel(230-400 mesh, 5×5 cm) with 1:1 acetone:CHCl₃ (500 mL). The filtrate wasconcentrated and applied to a silica gel column (230-400 mesh, 5×18 cm),eluted with acetone:CHCl₃ (1:2, 1.5 L), followed by acetone:CHCl₃ (1:1,1.5 L). Pure product was obtained from the column as a white powder 0.76g (100%) after drying and was shown to be the desired 2'-O-pivaloylderivative: m.p.: 83°-85° C. (uncorrected); UV λ_(max) (.di-electcons.): pH=7.00: 279.7 nm (8,100), 247.9 nm (8,800); 0.1N CHl: 286.6(7,300), 244.7 (6,200); 0.1N NaOH: 279.7 (8,000), 248.8 (7,900); MS(EI): m/z 250 (C₁₀ H₁₂ N₅ O₃), 232 (C₁₀ H₁₀ N₅ O₂), 217 (C₁₀ H₁₇ N₅),208 (C₈ H₁₀ N₅ O₂), 194 (C₇ H₈ N₅ O₂), 165 (C₆ H₇ N₅ O), 135 (C₅ H₄ N₄O₄), 101 (C₅ H₉ O₂), 85 (C₅ H₉ O); IR (KBr): 1734.2, 1616.3 and 1589.4cm⁻¹ ; ¹ H-NMR (Me₂ SO-d₆): δ7.97 (s, 1 H, H-2), 6.47 (br.s, 2 H, NH₂),6.26 (d, 1 H, H-1', J=5.9 Hz), 5.79 (d, 1 H, 3'-OH, J=5.3 Hz), 5.23 (dd,1 H, H-2', J_(1'),2' =5.9 Hz, J_(2'),3' =5.2 Hz), 5.06 (t, 1 H, 5'-OH,J=5.5 Hz), 4.37 (ddd, 1 H, H-3', J_(3'),3' 5.3 Hz, J_(2'),3' =5.2 Hz),J_(3'),4' 6.9 Hz), 3.92 (s, 3 H, Pur-OCH₃), 3.84-3.79 (m, 1 H, H-4'),3.68-3.62 (m, 2 H, H-5').

Anal. Calcd. for C₁₆ H₂₃ N₅ O₆.0.40 CHCl₃ : Calcd: C, 45.90; H, 5.50; N,16.32. Found: C, 46.03; H, 5.69; N, 16.03.

EXAMPLE 9M:2-Amino-9-(2-O-benzoyl-3,5-di-O-tert-butyldimethylsilyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-[(3,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-6-methoxy-9H-purine (1.3 g, 2.5 mmol) was weighed in to a flame dried 250 mL roundbottom Flask. 4-N,N-Dimethylaminopyridine (0.05 g, 0.4 mmol) and benzoicanhydride (0.67 g, 3.0 mmol) were added and the flask was flushed withargon and sealed with a septum. Dry acetonitrile (30 mL) andtriethylamine (5.0 mL) were then added, and the mixture stirred at roomtemperature. After 18 hours, the reaction mixture was concentrated andthe residue was taken up in ethyl acetate (250 mL) and extracted with H₂O (3×50 mL). The ethyl acetate was dried (MgSO₄), filtered, andconcentrated to give 1.76 g of a yellow oil. A 250 mg portion of thismaterial was purified on a Chromatotron® (Harrison Scientific) fittedwith a 2 mm silica gel rotor. The rotor was eluted with acetone: CHCl₃(1:10). The product off the Chromatotron® was a white solid (0.21 g):m.p.: 129°-131° C. (uncorrected); MS (EI): m/z 629 (C₃₀ H₄₇ N₅ O₆ Si₂),572 (C₂₆ H₄₇ N₅ O₆ Si₂), 440 (C₂₀ H₂₂ N₅ O₅ Si), 312 (C₁₅ H₁₄ N₅ O₃),261 (C₁₁ H₂₅ O₃ Si₂), 231 (C₉ H₁₉ O₃ Si₂), 194 (C₇ H₈ N₅ (₂), 166 (C₆ H₈N₅ O), 105 (C₇ H₅ O). ¹ H-NMR (CDCl₃): δ8.07 (s, 1 H, H-8), 7.67 (dd, 2H, Ar-H, J=1.0 Hz, J=8.2 Hz), 7.50 (tt, 1 H, Ar-H, J=2.0 Hz, J=8.0 Hz),7.30 (t, 2 H, Ar-H, J=7.5 Hz), 6.48(d, 1 H, H-1', J=5.5 Hz), 5.63 (t, 1H, H-2', J=5.5 Hz), 4.74 (t, 1 H, H-3', J=5.6 Hz), 4.68 (br.s, 2 H,NH₂), 3.98 (s, 3 H, --OCH₃), 4.00-3.80 (m, 3 H, H-4' and H-5'), 0.92 (s,9 H, --SiC(CH₃)₃), 0.88 (s, 9 H, --SiC(CH₃)₃), 0.12 (s, 3 H, --Si(CH₃)),0.09 (s, 3 H, --Si(CH₃)), 0.08 (s, 3 H, --Si(CH₃)), 0.06 (s, 3 H,--Si(CH₃)).

Anal. Calcd. for C₃₀ H₄₇ N₅ O₆ Si₂ :Calcd: C, 57.20; H, 7.52; N, 11.12.Found: C, 57.42; H, 7.57; N, 11.12.

EXAMPLE 9N: 2-Amino-9-(2-O-benzoyl-β-D-arabinofuranosyl)-6-methoxy-9H-purine

2-Amino-9-[(2-O-benzoyl-3,5-di-O-tert-butyldimethylsilyl)-β-D-arabinofuranosyl]-6-methoxy-9 H-purine (1.26 g, 2.0 mmol) wastaken up in tetrahydrofuran (THF, 40 mL) and cooled in an ice bath to 5°C. Acetic acid (0.06 mL, 10 mmol) was added, followed bytetrabutylammonium fluoride (TBAF) as a 1M solution in THF (10 mL, 10mmol). After 24 hours at 5° C., the reaction mixture was diluted withCHCl₃ (40 mL) and passed through a pad of silica gel (230-400 mesh, 5×5cm) with 1:1 acetone:CHCl₃ (500 mL). The filtrate was concentrated andapplied to a silica gel column (230-400 mesh, 5×18 cm). The column waseluted with acetone:CHCl₃ (1:2, 1 L) followed by acetone:CHCl₃ (1:1, 1.5L). Pure product was obtained from the column corresponding to materialwith an R_(f) =0.33 in acetone:CHCl₃ (1:1). This material was a whitepowder 0.74 g (90%) after drying and was shown to be the desired2'-O-benzoyl derivative: m.p.: 82°-84° C. (uncorrected); UV λ_(max)(.di-elect cons.): pH=7.00: 279.1 nm (8,600), 237.5 nm (17,800); 0.1NHCl: 277.8 (10,000), 245 (sh) (10,800); 0.1N NaOH: 286.1 (7,600), 236.4(17,000). MS (EI): m/z 401 (M, C₁₈ H₁₉ N₅ O₆), 371 (C₁₇ H₁₇ N₅ O₅), 312(C₁₅ H₁₄ N₅ O₃), 279 (C₁₁ H₁₃ N₅ O₄), 237 (C₁₂ H₁₃ O₅), 220 (C₁₂ H₁₂N₄), 208 (C₈ H₁₀ N₅ O₂), 194 (C₇ H₈ N₅ O₂), 165 (C₆ H₇ N₅ O), 135 (C₅ H₅N₅), 105 (C₇ H₅ O); IR(KBr): 1725.3, 1613.6 and 1588.9 cm⁻¹ ; ¹H-NMR(Me₂ SO-d₆): δ8.04(s, 1 H, H-2), 7.70-7.57 (m, 3 H, Ar-H),7.47-7.39 (m, 2 H, Ar-H), 6.44 (br.s, 2 H, NH₂), 6.39 (d, 1 H, H-1',J=5.6 Hz), 5.90 (d, 1 H, 3'-OH, J=4.9 Hz), 5.48 (t, 1 H, H-2', J=5.3Hz), 5.07 (t, 1 H, 5'-OH, J=5.6 Hz), 4.51 (apparent quartet, 1 H, H-3',J_(3'),3' -OH=4.9 Hz, J_(2'),3' =5.6 Hz, J_(3'), 4' =5.1 Hz), 3.87 (s, 3H, Pur-OCH₃), 3.94-3.83 (m, 1 H, H-4'), 3.77-3.66 (m, 2 H, H-5').

Anal. Calcd. for C₁₈ H₁₉ N₅ O₆.0.20 C₃ H₆ O.0.50 CHCl₃ : Calcd: C,48.53; H, 4.41; N, 14.82. Found: C, 48.68; H, 4.54; N, 14.96.

EXAMPLE 9O: 2-Amino-6-methoxy-9-(5-O-valeryl-β-D-arabinofuranosyl)-9H-purine

2-Amino-6-methoxy-9-β-O-arabinofuranosyl-9 H-purine (1.0 g, 3.2 mmol)was suspended in 40 ml of pyridine that contained 300 μL of H₂ O and 2.0mL of trichloroethyl valerate (Trichloroethyl valerate was synthesizedby addition of 36 g of valeryl chloride (Aldrich) over 30 minutes to 45g of trichioroethanol (Aldrich) in 50 mL of pyridine at 0° C. Theproduct was purified by successive washing with 2×250 ml aliquots of H₂O, 5% NaHCO₃, and H₂ O, ¹ H-NMR (200 MHz, CDCl₃): δ4.74 (s, 2 H, Cl₃ CH₂--), 2.48 (t, 2 H, J=7.6 Hz, CH₃ CH₂ CH₂ CH₂ CO₂ --), 1.68 (m, 2 H, CH₃CH₂ CH₂ CH₂ CO₂ --), 1.53 (M, 2 H, CH₃ CH₂ CH₂ CH₂ CO₂ --), 0.93 (t, 3H, J=7.2 Hz, CH₃ CH₂ CH₂ CH₂ CO₂ --)). The reaction was initiated with0.100 g of subtilisin (Sigma Chemical Co., St. Louis, Mo., P-5380, lot#38F-0356), which had been activated by dissolving 1 g of the enzyme in20 ml of 0.1M potassium phosphate at pH 7.8 and lyophilizing to dryness.After stirring for 24 hours at 40° C., the reaction was quenched byfiltering off the enzyme and the solvent was removed in vacuo. The crudeproduct was purified by chromatography on a 4.5×25 cm silica gel columnwith CH₂ Cl₂ :CH₃ OH (90:10) as the eluant. Product fractions werepooled and lyophilized from water to yield 0.85 g of the desired productas a white powder; m.p. 105° C.; TLC R_(f) =0.39(silica gel; CH₂ Cl₂:CH₃ OH (90:10)); UV λ_(max) (.di-elect cons., mM⁻¹ cm⁻¹) at pH 7.0, 279nm (9.3); MS (Cl) 382 (M+1), 280 (M-C₅ H₉ CO₂). ¹ H-NMR (200 MHz,DMSO-d₆): δ7.83 (s, 1 H, H₈), 6.45 (s, 2 H, 2-NH₂), 6.15 (d, 1 H, J=3.7Hz, H₁ '), 5.76 (d, 1 H, J=4.2 Hz, 2'-OH), 5.65 (d, 1 H, J=3.5 Hz,3'OH), 4.28 (m, 2 H, H₂ ' and H₃ '), 4.08 (m, 2 H H_(5')), 3.94 (s, 3 H,--OCH₃) 3.92 (m, 1 H, H_(4')), 2.29 (t, 2 H, J=7.1 Hz, CH₃ CH₂ CH₂ CO₂--), 1.49 (m, 2 H, CH₃ CH₂ CH₂ CH₂ CO₂ --) 1.28 (m, 2 H CH₃ CH₂ CH₂ CH₂CO₂₋₋), 0.83 (t, 3 H, J=7.2 Hz, CH₃ CH₂ CH₂ CH₂ CO₂₋₋).

Anal. Calcd. for C₁₆ H₂₃ N₅ O₆.0.36 H₂ O: Calcd: C, 49.54; H, 6.16; N,18.05. Found: C, 49.52; H, 6.15; N, 18.10.

EXAMPLE 9P: 2-Amino-6-methoxy-9-(5-O-acetyl-β-D-arabinofuranosyl)-9H-purine

2-Amino-6-methoxy-9-b-D-arabinofuranosyl-9 H-purine (1.0 g, 3.3 mmol)was suspended in 40 ml of pyridine that contained 300 μL of H₂ O and 1ml of trichloroethyl propionate (Trichloroethyl acetate was synthesizedas follows: 2,2,2-trichloroethanol (19.1 mL, 197.1 mmole) and drypyridine (40 mL) were placed in a three-neck, round-bottom flaskequipped with argon inlet valve, thermometer, dropping funnel, magneticstirring, and ice/H₂ O bath. Acetyl chloride (14.5 mL, 199.8 mmole) wasplaced in the dropping funnel and added over a ten minute period,keeping the temperature below 25° C. while stirring under argon. Theresulting product was washed with H₂ O (2×100 mL), 5% NaHCO₃ (2×100 mL),and H₂ O (2×100 mL). The organic layer was dried over MgSO₄, thenfiltered through Whatman #1 paper, and distilled under vacuum. A middlecut of 5.18 g was the desired material, contaminated with a small amountof acetic acid: ¹ H-NMR (CDCl₃): δ4.73 Cs, 2 H, CH₂ O), 2.20 Cs, 3 H,CH₃ CO); MS (Cl, CH₄): m/z 197 (M+H, C₄ H₅ O₂ ³⁷ Cl₃), 195 (M+H, C₄ H₅O₂ ³⁷ Cl₂ ³⁵ Cl), 193 (M+H, C₄ H₅ O₂ O³⁵ Cl₂ ³⁷ Cl), 191 (M+H, C₄ H₅ O₂³⁵ Cl₃), 159 (195-HCl, C₄ H₄ O₂ ³⁷ Cl₂), 157 (193-HCl, C₄ H₄ O₂ ³⁷ Cl³⁵Cl), 155 (191-HCl, C₄ H₄ O₂ ³⁵ Cl₂); (EI): m/z 195 (M+H), 193 (M+H), 191(M+H), 157 (193-CHl), 155 (191-HCl). Analysis for C₄ H₅ Cl₃ O₂ +0.054mole CH₃ COOH: C, 25.35; H, 2.70; Cl, 54.62. Found: C, 25.57; H, 2.72;Cl, 54.66.). The reaction was initiated with 0.050 g of subtilisin(Sigma Chemical Co., St. Louis, Mo., P-5380, lot#38F-0356,), which hadbeen activated by dissolving 1 g of the enzyme in 20 ml of 0.1Mpotassium phosphate at pH 7.8 and lyophilizing to dryness. Afterstirring for 23 hours at 40° C. an additional 50 mg of subtilisin and 2mL of trichioroethyl acetate were added to the reaction. After stirringat 40° for an additional 24 hours the reaction was quenched by filteringoff the enzyme and the solvent was removed in vacuo. The crude productwas purified by chromatography on a 4.5×25 cm silica gel column with CH₂Cl₂ :CH₃ OH (9:1) as eluant. Product fractions were pooled andlyophilized from water to yield 0.28 g of the desired product as a whitepowder. TLC R_(f) =0.35 (silica gel; CH₂ Cl₂ :CH₃ OH (9:1)); UV λ_(max)(.di-elect cons., mM⁻¹ cm⁻¹) at pH 7.0, 279 nm (8.8). ¹ H-NMR (200 MHz,DMSO-d₆): δ7.83 (s, 1 H, H₈), 6.45 (s, 2 H, 2-NH₂), 6.14 (d, 1 H, J=3.7Hz, H_(1')), 5.75 (d, 1 H, J=4.5 Hz, 2'-OH), 5.65(d, 1 H, J=3.7 Hz,3'-OH), 4.26 (m, 2 H, H_(2') and H_(3')), 4.07 (m, 2 H, H_(5')) 3.94 (s,3 H, --OCH₃) 3.92 (m, 1 H, H_(4')), 2.01 (s, 3 H, CH₃ CO₂₋₋); MS (Cl)340 (M+1), 280 (M-CH₃ CO₂).

Anal. Calcd. for C₁₄ H₁₉ N₅ O₆.0.52 H₂ O: Calcd: C, 44.77; H, 5.22; N,20.12. Found: C, 44.79; H, 5.21; N, 20.09.

EXAMPLE 9Q:2-Amino-6-methoxy-9-(5-O-(4-methoxy-4-oxobutyryl)-β-D-arabinofuranosyl)-9H-purine

2-Amino-6-methoxy-9-β-D-arabinosuranosyl-9 H-purine (1.0 g, 3.2 mmol)was suspended in 40 mL of pyridine that contained 300 μL of H₂ O and 2ml of trichloroethyl methylsuccinate. (Trichloroethyl methylsuccinatewas synthesized by addition of 25 g of 3-carbomethoxypropionyl chloride(Aldrich) over 30 minutes to 15.8 g of trichloroethanol (Aldrich) in 40ml of pyridine at 0° C. The product was purified by successive washingwith 2×200 ml aliquots of H₂ O, 5% NaHCO₃, and H₂ O and then dried overNa₂ SO₄. ¹ H-NMR (200 MHz, CDCl₃): δ4.75 (s, 2 H, Cl₃ CH₂₋₋), 3.7 (s, 3H, CH₃ OC(O).), 2.77 (m, 4 H, --OC(O)CH₂ CH₂ CO₂₋₋)). The reaction wasinitiated with 0.050 g of subtilisin (Sigma Chemical Co., St. Louis,Mo., P-5380, lot #38F-0356), which had been activated by dissolving 1 gof the enzyme in 20 ml of 0.1M potassium phosphate at pH 7.8 andlyophilizing by filtering off the enzyme and the solvent was removed invacuo. The crude product was purified by chromatography on a 4.5×25 cmsilica gel column with CH₂ Cl₂ :CH₃ OH (90:10) as the eluant. Productfractions were pooled and lyophilized from water to yield 1.01 g of thedesired product as a white powder. TLC R_(f) =0.31 (silica gel; CH₂ Cl₂:CH₃ OH (90:10)); UV λ_(max) (.di-elect cons., mM⁻¹ cm⁻¹) at pH 7.0, 277nm (9.6). ¹ H-NMR (200 MHz, DMSO-d₆): δ7.83 (s, 1 H, H₈), 6.45 (s, 2 H,2-NH₂), 6.15 (d, 1 H, J=3.7 Hz, H₁), 5.75 (d, 1 H, J=4.3 Hz, 2'-OH),5.65 (d, 1 H, J=3.7 Hz, 3'-OH), 4.28 (m, 2 H, H_(2') and H_(3')), 4.08(m, 2 H, H_(5')), 3.95 (s, 3 H, --OCH₃) 3.91 (m, 1 H, H_(4')), 3.51 (s,3 H, CH₃ OC(O)--), 2.56 (s, 4H, --OC(O)CH₂ CH₂ C(O)O--); MS (Cl) 412(M+1), 280 (M-C₅ H₇ O₄).

Anal. Calcd. for C₁₆ H₂₁ N₅ O₈.0.40 H₂ O: Calcd: C, 45.64; H, 5.28; N,16.63. Found: C, 45.62; H, 5.21; N, 16.67.

EXAMPLE 10: 9-β-D-Arabinofuranosyl-6-n-propoxy-9 H-purine

6-n-Propoxypurine (5.6 mmoles, 1 g, Sigma Chemicals, St. Louis Mo.) wascombined with 545 ml of a uracil arabinoside solution (10.1 mmoles)in 10mM potassium phosphate and 7% n-propanol (v/v). Purified uridinephosphorylase (680 I.U.) and purine nucleoside phosphorylase (12000I.U.) were added and the reaction stirred at 35° C. The reaction wasfiltered after 58 days and the filtrate stored at 3° C. for 20 hours.The resulting precipitate was collected by centrifugation, dissolved in30% n-propanol/water (v/v), and chromatographed on a column ofDowex-1-formate resin (2.5×5 cm) after adjusting the pH to 10.5 withconcentrated ammonium hydroxide. The column was eluted with 30%n-propanol/water (v/v) and fractions containing product were combinedand solvent removed in vacuo. The residue was dissolved in n-propanoland chromatographed on a column containing BioRad P-2 (5×90 cm). Thecolumn was eluted with 30% npropanol/water (v/v). Product-containingfractions were combined and after removing the solvent under vacuum theresidue was dissolved in water and chromatographed on a columncontaining BioRad P-2 (5×90 cm). The column was eluted with water.Product containing fractions were combined and after lyophilization,yielded 0.758 g of 9-β-D-arabinofuranosyl-6-n-propoxy-9 H-purine thatanalyzed as a monohydrate. NMR and mass spectrometry were consistentwith the structure.

Anal. Calcd. for C₁₃ H₁₈ N₄ O₅.H₂ O: Calcd: C, 47.56; H, 6.14; N, 17.06.Found: C, 47.63; H, 6.13; N, 17.11.

EXAMPLE 11: Tablet Formulations

The following formulations A and B are prepared by wet granulation ofthe ingredients with a solution of povidone, followed by addition ofmagnesium stearate and compression.

    ______________________________________                                                         mg/tablet                                                                             mg/tablet                                            ______________________________________                                        Formulation A                                                                 (a) Active Ingredient                                                                            250       250                                              (b) Lactose B.P.   210        26                                              (c) Povidone B.P.   15        9                                               (d) Sodium Starch Glycollate                                                                      20        12                                              (e) Magnesium Stearate                                                                            5         3                                                                  500       300                                              Formulation B                                                                 (a) Active Ingredient                                                                            250       250                                              (b) Lactose B.P.   150       --                                               (c) Avicel PH 101   60        26                                              (d) Povidone B.P.   15        9                                               (e) Sodium Starch Glycollate                                                                      20        12                                              (f) Magnesium Stearate                                                                            5         3                                                                  500       300                                              ______________________________________                                                         mg/tablet                                                    ______________________________________                                        Formulation C                                                                 Active Ingredient  100                                                        Lactose B.P.       200                                                        Povidone B.P.       50                                                        Sodium Starch Glycollate                                                                          5                                                         Magnesium Stearate  4                                                                            359                                                        ______________________________________                                    

Tablets are prepared from the foregoing ingredients (C) by wetgranulation followed by compression. In an alternative preparation thePovidone B.P. may be replaced by Polyvinylpyrrolidone.

The following formulations, D and E, are prepared by direct compressionof the admixed ingredients. The lactose in formulation E is of thedirect compression type (Dairy Crest-"Zeparox").

    ______________________________________                                                          mg/capsule                                                  ______________________________________                                        Formulation D                                                                 Active Ingredient   250                                                       Pregelatinized Starch NF15                                                                        150                                                                           400                                                       Formulation E                                                                 Active Ingredient   250                                                       Lactose             150                                                       Avicel              100                                                                           500                                                       ______________________________________                                    

Formulation F (Controlled Release Formulation)

The formulation is prepared by wet granulation of the ingredients(below) with a solution of povidone followed by the addition ofmagnesium stearate and compression.

    ______________________________________                                                             mg/tablet                                                ______________________________________                                        (a)     Active Ingredient  500                                                (b)     Hydroxypropylmethylcellulose                                                                     112                                                        (Methocel K4M Premium)                                                (c)     Lactose B.P.        53                                                (d)     Povidone B.P.       28                                                (e)     Magnesium Stearate  7                                                                            700                                                ______________________________________                                    

Drug release takes place over a period of about 6-8 hours and iscomplete after 12 hours.

EXAMPLE 12: Capsule Formulations Formulation A

A capsule formulation is prepared by admixing the ingredients ofFormulation D in Example 12 above and filling into a two-part hardgelatin capsule. Formulation B (infra) is prepared in a similar manner.

    ______________________________________                                                          mg/capsule                                                  ______________________________________                                        Formulation B                                                                 (a) Active ingredient                                                                             250                                                       (b) Lactose B.P.    143                                                       (c) Sodium Starch Glycollate                                                                       25                                                       (d) Magnesium Stearate                                                                             2                                                                            420                                                       Formulation C                                                                 (a) Active ingredient                                                                             250                                                       (b) Macrogol 4000 B.P.                                                                            350                                                                           600                                                       ______________________________________                                    

Capsules are prepared by melting the Macrogol 4000 BP, dispersing theactive ingredient in the melt and filling the melt into a two-part hardgelatin capsule.

    ______________________________________                                                      mg/capsule                                                      ______________________________________                                        Formulation D                                                                 Active ingredient                                                                             250                                                           Lecithin        100                                                           Arachis Oil     100                                                                           450                                                           ______________________________________                                    

Capsules are prepared by dispersing the active ingredient in thelecithin and arachis oil and filling the dispersion into soft, elasticgelatin capsules.

Formulation E (Controlled Release Capsule)

The following controlled release capsule formulation is prepared byextruding ingredients (a), (b) and (c) using an extruder, followed byspheronization of the extrudate and drying. The dried pellets are thencoated with release-controlling membrane (d) and filled into atwo-piece, hard gelatin capsule.

    ______________________________________                                                          mg/capsule                                                  ______________________________________                                        (a) Active Ingredient                                                                             250                                                       (b) Microcrystalline Cellulose                                                                    125                                                       (c) Lactose B.P.    125                                                       (d) Ethyl Cellulose  13                                                                           513                                                       ______________________________________                                    

EXAMPLE 13: Ophthalmic Solution

    ______________________________________                                        Active Ingredient    0.5                                                      Sodium chloride, analytical grade                                                                  0.9       g                                              Thiomersal           0.001     g                                              Purified water to    100       mL                                             pH adjusted to       7.5                                                      ______________________________________                                    

EXAMPLE 14: Injectable Formulation

    ______________________________________                                        Active Ingredient          0.200  g                                           Sterile, pyrogen free phosphate buffer (pH 7.2) to                                                       10     mL                                          ______________________________________                                    

The active ingredient is dissolved in most of the phosphate buffer(35°-40° C.), then made up to volume and filtered through a sterilemicropore filter into a sterile 10 mL amber glass vial (type 1) andsealed with sterile closures and overseals.

EXAMPLE 15: Intramuscular Injection

    ______________________________________                                        Active Ingredient                                                                             0.20          g                                               Benzyl Alcohol  0.10          g                                               Glycofurol 75   1.45          g                                               Water for Injection                                                                           q.s. to 3.00  mL                                              ______________________________________                                    

The active ingredient is dissolved in the glycofurol. The benzyl alcoholis then added and dissolved, and water added to 3 mL. The mixture isthen filtered through a sterile micropore filter and sealed in sterile 3mL amber glass vials (type 1).

EXAMPLE 16: Syrup Suspension

    ______________________________________                                        Active Ingredient                                                                              0.25          g                                              Sorbitol Solution                                                                              1.50          g                                              Glycerol         2.00          g                                              Dispersible Cellulose                                                                          0.075         g                                              Sodium Benzoate  0.005         g                                              Flavor, Peach 17.42.3169                                                                       0.0125        mL                                             Purified Water   q.s. to 5.00  mL                                             ______________________________________                                    

The sodium benzoate is dissolved in a portion of the purified water andthe sorbitol solution added. The active ingredient is added anddispersed. In the glycerol is dispersed the thickener (dispersiblecellulose). The two dispersions are mixed and made up to the requiredvolume with the purified water. Further thickening is achieved asrequired by extra shearing of the suspension.

EXAMPLE 17: Suppository

    ______________________________________                                                               mg/suppository                                         ______________________________________                                        Active ingredient (63 μM)*                                                                           250                                                 Hard Fat, BP (Witepsol H15 - Dynamit Nobel)                                                            1700                                                                          1950                                                 ______________________________________                                    

One-fifth of the Witepsol H15 is melted in a steam-jacketed pan at 45°C. maximum. The active ingredient is sifted through a 200 μM sieve andadded to the molten base with mixing, using a silverson fitted with acutting head, until a smooth dispersion is achieved. Maintaining themixture at 45° C., the remaining Witepsol H15 is added to the suspensionand stirred to ensure a homogenous mix. The entire suspension is passedthrough a 250 μM stainless steel screen and, with continuous stirring,is allowed to cool to 40° C. At a temperature of 38° C. to 40° C., 2.02g of the mixture is filled into suitable plastic molds. Thesuppositories are allowed to cool to room temperature.

EXAMPLE 18: Pessaries

    ______________________________________                                                          mg/pessary                                                  ______________________________________                                        Active ingredient (63 μM)*                                                                     250                                                       Anhydrate Dextrose  380                                                       Potato Starch       363                                                       Magnesium Stearate   7                                                                            1000                                                      ______________________________________                                    

The above ingredients are mixed directly and pessaries prepared bydirect compression of the resulting mixture.

EXAMPLE 19: Determination of Anti-Varicella-Zoster Virus Activity

The inhibitory effects of compounds on the replication of VZV (Okastrain) were assessed by an ELISA procedure (Berkowitz, F. E., andLevin, M. J. (1985) Antimicrob. Agents and Chemother. 28, 207-210)thatwas modified as follows. Infections were initiated in the presence ofdrug, rather than before drug addition. At the end of the three-dayincubation of drug and virus with uninfected cells (human diploidfibroblasts, strain MRC-5), the 96-well plates were centrifuged for 5minutes at 200×g to sediment detached cells prior to glutaraldehydefixation. The present ELISA used an alkaline phosphatase-conjugatedanti-human IgG as the second antibody. The rate of cleavage ofp-nitrophenyl phosphate by bound alkaline phosphatase was determined asdescribed elsewhere (Tadepalli, S. N., Quinn, R. P., and Averett, D. R.(1986) Antimicrob. Agents and Chemother. 29, 93-98). Uninfected cellswere used to obtain the blank reaction rates, which were subtracted fromthe rates obtained with the virus present. This assay was suitable todetect progeny virus in cultures that were initially infected with 15 to3600 infectious particles per cell.

The anti-varicella zoster virus activity of the compound of Example 9 is14 μM.

We claim:
 1. 2-Amino-6-methoxy-9-(5-O-propionyl-β-D-arabinofuranosyl-9H-purine.
 2. 2-Amino-6-methoxy-9-(5-O-butyryl-β-D-arabinofuranosyl-9H-purine.